dm crypt: fix error with too large bios

When dm-crypt processes writes, it allocates a new bio in
crypt_alloc_buffer().  The bio is allocated from a bio set and it can
have at most BIO_MAX_PAGES vector entries, however the incoming bio can be
larger (e.g. if it was allocated by bcache).  If the incoming bio is
larger, bio_alloc_bioset() fails and an error is returned.

To avoid the error, we test for a too large bio in the function
crypt_map() and use dm_accept_partial_bio() to split the bio.
dm_accept_partial_bio() trims the current bio to the desired size and
asks DM core to send another bio with the rest of the data.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # v3.16+

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index eedba67..d609566 100644 (file)
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -1924,6 +1924,13 @@ static int crypt_map(struct dm_target *ti, struct bio *bio)
                return DM_MAPIO_REMAPPED;
        }
 
+       /*
+        * Check if bio is too large, split as needed.
+        */
+       if (unlikely(bio->bi_iter.bi_size > (BIO_MAX_PAGES << PAGE_SHIFT)) &&
+           bio_data_dir(bio) == WRITE)
+               dm_accept_partial_bio(bio, ((BIO_MAX_PAGES << PAGE_SHIFT) >> SECTOR_SHIFT));
+
        io = dm_per_bio_data(bio, cc->per_bio_data_size);
        crypt_io_init(io, cc, bio, dm_target_offset(ti, bio->bi_iter.bi_sector));
        io->ctx.req = (struct skcipher_request *)(io + 1);